This invention relates to a process for the production of the methyl ethyl ketone cynohydrin of the formula: 
This cyanohydrin is a starting product for the production of azo polymerization triggers.
To the knowledge the filling company, the preparation of the methyl ethyl ketone cyanohydrin is not very specifically described in literature. It is possible to simply cite Example III of International Application WO 85/00166 that describes the preparation of this cyanohydrin by reaction of the methyl ethyl ketone with sodium cyanide and hydrochloric acid in water. The drawbacks of this method are the presence of water and salt in stoichiometric amounts.
According to this invention, a process is proposed to obtain the cyanohydrin in question, with fast kinetics, whereby this process is characterized by the fact that the hydrocyanic acid and the methyl ethyl ketone are reacted in the presence of diethylamine as a catalyst.
If a comparison is made with the same reaction that is conducted with the use of a solution of soda as a catalyst, an acceleration of the reaction speed is noted as a first advantage. The second advantage that can be mentioned is that, taking into account the better activity of the diethylamine relative to the soda, it is possible to use less of it, which makes it possible to limit the subsequent supply of sulfuric acid that is necessary to neutralize the catalyst before purification of the cyanohydrin (with soda, the risk of crystallization of the Na2SO4 salt is real and optionally calls for a filtration, which is not the case with a small amount of amine). It is also possible to emphasize that it is not necessary to work in the presence of traces of water that are supplied by the soda, which prevents possible segregations and limits the contents of water and hydrolysis products in the pure cyanohydrin (formic acid).
The reagents are generally initially introduced into the reactor, and diethylamine is added there while being stirred; it is also possible to add one reagent into the other in the presence of diethylamine. The reaction is balanced.
The diethylamine is preferably introduced at a rate of 10xe2x88x923 to 5xc3x9710xe2x88x923 mol, in particular at a rate of 1.5xc3x9710xe2x88x923-3xc3x9710xe2x88x923 mol per mol of reagent too little (hydrocyanic acid or methyl ethyl ketone).
According to other characteristics of this invention, the reaction is conducted at atmospheric pressure at a temperature of xe2x88x9220 to 40xc2x0 C., in particular from xe2x88x9210 to 30xc2x0 C. at a pH of 7 to 9, in particular from 7.5 to 8.5, with an HCN/methyl ethyl ketone molar ratio of between 0.90 and 1.10, in particular between 0.95 and 1.05, and for a period of 1 to 4 hours, in particular from 1 to 2 hours.
The purification of the cyanohydrin that is obtained consists in neutralizing the diethylamine (for example with sulfuric acid), acidifying to no longer shift the balance and eliminating the HCN and the methyl ethyl ketone (in excess or having not reacted) by distillation under reduced pressure, by conforming to the decomposition temperature of the cyanohydrin.
The following examples illustrate this invention without, however, limiting its scope.